easy/productive = You can not beat Teiid in these respect. Teiid has done the hard work already it can save many months development (if not more) if you were to home grow the solution. Do not underestimate the complexity of data integration. We provide a flexible and well defined way integrate your sources along with tooling and monitoring etc. Ultimately, if you understand product it makes it easy and productive. Redhat is in works to provide commercial support for this project in very soon (if needed by your company to deploy in production environment).

performent = In most scenarios we can match or beat user scenarios. However since Teiid accounts for all the possible scenarios, one could always write code to match their exact usecase and might get little better numbers. We provide facilities like cost based planning, join hints, buffering, batching and caching to improve performance.

Finally, it is relative to what you are comparing with? Do you have some numbers you think are better with custom coding or other products than Teiid. We are open for suggestions from our community to improve it. Just note this process is always improving and we are providing more and more features.

You can code the stored procedures in Teiid using the SQL/XML that returns XML object, and write your own web-service to call/execute the procedure or you can use Designer, to generate web-service model on top of this procedure and generate the war file.

Another way is based on a schema file, create a XML model and provide transformations to generate the needed XML, then use a web services model on top this model and expose the web service by generating the WAR file.

Here are some links for the Web Service stuff. Also, check the Teiid Designer documentation on the XML stuff.